Ink for inkjet recording, ink set for inkjet recording and inkjet recording method

ABSTRACT

The present invention provides an ink for inkjet recording capable of giving a color image having excellent fastness to ozone gas and provides an ink set for inkjet recording and an inkjet recording method, which can form an image having excellent color reproducibility and high light fastness, in which the ink for inkjet recording comprises an azo dye having a specific structure; an ink set for inkjet recording, comprising a yellow ink, a magenta ink and a cyan ink as minimum constituent elements, wherein these inks comprises the above-described azo dye; and an inkjet recording method using the ink for inkjet recording or the ink set for inkjet recording.

TECHNICAL FIELD

The present invention relates to an ink and an ink set for inkjetrecording, which ensure excellent image fastness, and also relates to aninkjet recording method using the ink or ink set.

BACKGROUND ART

In recent years, the image recording material is predominatedparticularly by a material for forming a color image. More specifically,an inkjet system recording material, a thermal transfer-type imagerecording material, a recording material using an electrophotographicsystem, a transfer system silver halide photographic material, aprinting ink, a recording pen and the like are popularly used.

In these color image recording materials, three primary color dyes (dyesor pigments) for a so-called subtractive color mixing method are usedfor reproducing or recording a full color image, however, a dye havingabsorption properties capable of realizing a preferred colorreproduction region and having fastness capable of enduring various useconditions is not found at present and improvements are keenly demanded.

The inkjet recording method has been abruptly spread and is furthergrowing because the material cost is low, high-speed recording can beobtained, noises are less generated at the recording and color recordingis easy.

The inkjet recording method includes a continuous system of continuouslyjetting out a liquid droplet and an on-demand system of jetting out aliquid droplet according to image information signals, and the ejectionsystem therefor includes a system of ejecting a liquid droplet byapplying a pressure using a piezoelectric element, a system of ejectinga liquid droplet by generating bubbles in ink using heat, a system ofusing an ultrasonic wave, and a system of ejecting a liquid droplet bysuction using an electrostatic force. The ink used for inkjet recordingincludes an aqueous ink, an oily ink and a solid (fusion-type) ink.

The coloring agent used in such an inkjet recording ink is required tohave high solubility or dispersibility in a solvent, enable high-densityrecording, provide good color, be fast to light, heat and active gasesin the environment (for example, NO_(x), oxidative gas (e.g., ozone) andSO_(x)), exhibit excellent fastness to water and chemicals, ensure goodfixing to an image-receiving material and less bleeding, give an inkhaving excellent storability, have high purity and no toxicity, and beavailable at a low cost. However, it is very difficult to find out acoloring agent satisfying these requirements in a high level. Inparticular, the coloring agent is strongly demanded to ensure good colorfor three primary colors, be fast to light, humidity and heat and at theprinting on an image-receiving material having an ink-accepting layercontaining a porous white inorganic pigment particle, be resistantagainst oxidative gases such as ozone in the environment.

Conventionally, azo dyes using a phenol, a naphthol or an aniline as thecoupling component have been widely used as the dye. However, these dyesall are very poor in the fastness to oxidative gases such as ozone.

DISCLOSURE OF THE INVENTION

An object of the present invention is to solve the above-describedproblems in conventional techniques and provide the following dye, ink,ink set and inkjet recording method. More specifically, the object ofthe present invention is to provide:

1) an azo dye capable of drastically solving the ozone discolorationcommon to various dyes,

2) an inkjet recording ink capable of giving a color image havingexcellent fastness to ozone gas, and

3) an ink set for inkjet recording and an inkjet recording method, whichcan form an image having excellent color reproducibility and high lightfastness.

As a result of extensive investigations on the reaction of azo dye andozone, the present inventors have found that azo dyes having lowreactivity with ozone have common characteristic features, that is,

(i) the reaction with ozone readily takes place in hydrazo-type dyes butnot in azo-type dyes, and

(ii) when a hydrogen atom is present at the α-position of an alkylgroup-substituted heteroatom group such as amino group or ether groupused as an auxochrome, the dye exhibits high reactivity with ozone.

The alkyl group-substituted heteroatom group in which a hydrogen atom ispresent at the ax-position is a group shown as a substituent —X—CHRR′ inthe following formula (2):

In formula (2), A and B each have the same meanings as in the followingformula (1), X represents a nitrogen or oxygen atom substituted on thering of B at the conjugated position with respect to the azo group, andR and R′, which may be the same or different, each represents a hydrogenatom, an alkyl group, an aryl group or a heterocyclic group.

Furthermore, the present inventors have found that:

(iii) when an electron-withdrawing substituent is substituted, the azodye is retarded from the reaction with ozone.

Based on these findings, the present inventors have reached an azo dyehaving a specific structure where a hydroxyl group (including an enolgroup as a tautomer of ketone) at the conjugated position of azo group,which gives rise to generation of a hydrazo-type dye, is eliminated,hydrogen at the a-position as in formula (2) is not present andpreferably, an electron-withdrawing group is substituted, and thepresent invention has been accomplished.

More specifically, the present invention provides an ink and an ink setfor inkjet recording, having the following constitutions, and an inkjetrecording method.

1. An ink for inkjet recording, comprising at least one compoundselected from azo dyes represented by the following formula (1):A−N=N−Bwherein A and B each independently represents an aromatic group, or a 5-or 6-membered unsaturated heterocyclic group, provided that asubstituent on each ring of A and B, which is located at a conjugatedposition with respect to the azo group, satisfies the followingconditions (a) to (c):

(a) the substituent is not a hydroxyl group,

(b) when the substituent is an amino group, the amino group does nothave a hydrogen atom at the α-position, and

(c) when the substituent is an ether group, the ether group does nothave a hydrogen atom at the α-position.

2. The ink for inkjet recording as described in the item 1, wherein atleast one of A and B in the formula (1) represents a 5- or 6-memberedunsaturated heterocyclic group.

3. The ink for inkjet recording as described in the item 1 or 2, whereinthe azo dye represented by the formula (1) contains anelectron-withdrawing group.

4. The ink for inkjet recording as described in any one of the items 1to 3, wherein the amino group not having a hydrogen atom at theα-position is an amino group substituted by a tertiary alkyl group, anaryl group, a heterocyclic group or an unsubstituted amino group.

5. The ink for inkjet recording as described in any one of the items 1to 4, wherein the ether group not having a hydrogen atom at theα-position is an aryloxy group or a heteryloxy group.

6. An ink set for inkjet recording, comprising:

a yellow ink containing at least one yellow dye;

a magenta ink containing at least one magenta dye; and

a cyan ink containing at least one cyan dye,

wherein at least one dye of the yellow, magenta and cyan dyes containsan azo dye represented by the following formula (1):A−N=N−Bwherein A and B each independently represents an aromatic group, or a 5-or 6-membered unsaturated heterocyclic group, provided that asubstituent on each ring of A and B, which is located at a conjugatedposition with respect to the azo group, satisfies the followingconditions (a) to (c):

(a) the substituent is not a hydroxyl group,

(b) when the substituent is an amino group, the amino group does nothave a hydrogen atom at the α-position, and

(c) when the substituent is an ether group, the ether group does nothave a hydrogen atom at the α-position.

7. The ink set for inkjet recording as described in the item 6, whereinat least one of A and B in the formula (1) represents a 5- or 6-memberedunsaturated heterocyclic group.

8. The ink set for inkjet recording as described in the item 6 or 7,wherein the azo dye represented by the formula (1) contains anelectron-withdrawing group.

9. The ink set for inkjet recording as described in any one of the items6 to 8,. wherein the amino group not having a hydrogen atom at thea-position is an amino group substituted by a tertiary alkyl group, anaryl group, a heterocyclic group or an unsubstituted amino group.

10. The ink set for inkjet recording as described in any one of theitems 6 to 9, wherein the ether group not having a hydrogen atom at theα-position is an aryloxy group or a heteryloxy group.

11. The ink set for inkjet recording as described in any one of theitems 6 to 10, wherein the cyan dye includes a cyan dye represented bythe following formula (3):

wherein X₁₁ to X₁₄ each independently represents an electron-withdrawinggroup having a up value of 0.40 or more; Y₁₁ to Y₁₈ each independentlyrepresents a monovalent substituent; M represents a hydrogen atom, ametal element or its oxide, hydroxide or halide; a₁₁ to a₁₄ eachindependently represents an integer of 1 or 2.

12. An ink set for inkjet recording, comprising:

a yellow ink containing at least one yellow dye;

a magenta ink containing at least one magenta dye;

a cyan ink containing at least one cyan dye; and

a black ink containing at least one black dye,

wherein at least one dye of the yellow, magenta, cyan and black dyescontains an azo dye represented by the following formula (1):A−N=N−Bwherein A and B each independently represents an aromatic group, or a 5-or 6-membered unsaturated heterocyclic group, provided that asubstituent on each ring of A and B, which is located at a conjugatedposition with respect to the azo group, satisfies the followingconditions (a) to (c):

(a) the substituent is not a hydroxyl group,

(b) when the substituent is an amino group, the amino group does nothave a hydrogen atom at the α-position, and

(c) when the substituent is an ether group, the ether group does nothave a hydrogen atom at the α-position.

13. An inkjet recording method comprising forming an image using the inkfor inkjet recording described in any one of the items 1 to 5.

14. An inkjet recording method comprising forming an image using the inkset for inkjet recording described in any one of the items 6 to 11.

15. An inkjet recording method comprising forming an image using the inkset for inkjet recording described in the item 12.

16. The inkjet recording method as described in the item 13, whichcomprises forming an image on an image-receiving material comprising asupport having thereon an image-receiving layer containing a whiteinorganic pigment particle.

17. The inkjet recording method as described in the item 14, whichcomprises forming an image on an image-receiving material comprising asupport having thereon an image-receiving layer containing a whiteinorganic pigment particle.

18. The inkjet recording method as described in the item 15, whichcomprises forming an image on an image-receiving material comprising asupport having thereon an image-receiving layer containing a whiteinorganic pigment particle.

By using the azo dye represented by formula (1), not only the reactivitywith ozone is greatly suppressed but also the light fastness isimproved. Particularly, when a full color ink comprising the azo dye ofthe present invention is used, the balance of the image as a whole isprevented from serious disruption due to discoloration by ozone or lightand a high-quality full color image is obtained. Furthermore, even inuse of inks differing in the density, which are recently used forenhancing the color reproducibility, no problem arises in the fastnessof light color ink. In addition, the stability of the dye itself isincreased, whereby the oxidation stability of ink is enhanced and theguarantee period as a commercial product can be elongated.

BEST MODES OF CARRYING OUT THE INVENTION

The present invention is described in detail below.

[Azo Dye]

In the present invention, an azo dye represented by the followingformula (1) is used.

Formula (1):A−N=N−Bwherein A and B may be the same or different and each represents anaromatic group or a 5- or 6-membered unsaturated heterocyclic group,provided that the substituent on the A and B rings, which is located atthe conjugated position with respect to the azo group, satisfies thefollowing conditions (a) to (c):

(a) the substituent is not a hydroxyl group,

(b) when the substituent is an amino group, the amino group does nothave hydrogen at the α-position, and

(c) when the substituent is an ether group, the ether group does nothave hydrogen at the α-position.

The aromatic group represented by A and B means an aryl group or asubstituted aryl group. The aryl group is preferably phenyl or naphthyl,more preferably phenyl. The number of carbon atoms in the aromatic groupis preferably from 6 to 20, more preferably from 6 to 16.

The 5- or 6-membered unsaturated heterocyclic group may have asubstituent. Examples of the unsaturated heterocyclic ring include athiophene ring, a furan ring, a pyrrole ring, a thiazole ring, anoxazole ring, an imidazole ring, an isothiazole ring, an isoxazole ring,a pyrazole ring, a thiadiazole ring, an oxadiazole ring, a triazolering, a pyridine ring, a pyridazine ring, a pyrimidine ring and apyrazine ring. Among these, preferred are a thiazole ring, anisothiazole ring, a pyrazole ring, a thiadiazole ring, a triazole ring,a pyridine ring and a pyrazine ring, more preferred are an isothiazolering, a pyrazole ring, a thiadiazole ring and a pyridine ring, and mostpreferred are a pyrazole ring, a 1,2,4-thiadiazole ring, a1,3,4-thiadiazole ring and a pyridine ring.

The substituents on the unsaturated heterocyclic ring may combine witheach other to form a condensed ring with the hydrocarbon ring or theunsaturated heterocyclic ring. The condensed ring may have a substituentthereon. In the case of a nitrogen-containing unsaturated heterocyclicring, the nitrogen atom may be quaternized. In the case of anunsaturated heterocyclic ring which can form a tautomer, even when onlyone of tautomers is described, the ring includes other tautomers.

Preferably, at least either one of A and B is an unsaturatedheterocyclic ring, and more preferably, both are an unsaturatedheterocyclic ring.

The conjugated position on the rings A and B with respect to the azogroup means, for example, an ortho- or para-position when A and B are aphenyl group. When A and B are not a phenyl group, the conjugatedposition means the same positional relationship as in the case of aphenyl group, namely, a position where a lone electron pair of theheteroatom can conjugate with the azo group when an auxochrome issubstituted.

When the auxochrome is an amino group, the amino group is an amino groupnot having hydrogen at the α-position. Specific examples thereof includean unsubstituted amino group and an amino group substituted by atertiary alkyl group, an aryl group or a heterocyclic group. Amongthese, preferred are an arylamino group, a diarylamino group, aheterylamino group and an arylheterylamino group.

When the auxochrome is an ether group, the ether group is an ether groupnot having hydrogen at the α-position. Specific examples thereof includean aryloxy group and a heteryloxy group, with an aryloxy group beingpreferred.

In the case where the dye is a water-soluble dye, the dye preferablyfurther has an ionic hydrophilic group as a substituent. Examples of theionic hydrophilic group as a substituent include a sulfo group, acarboxyl group, a phosphono group and a quaternary ammonium group. Amongthese ionic hydrophilic groups, preferred are a carboxyl group, aphosphono group and a sulfo group, more preferred are a carboxyl groupand a sulfo group. The carboxyl group, the phosphono group and the sulfogroup each may be in the form of a salt and examples of the counter ionfor forming the salt include ammonium ion, alkali metal ion (e.g.,lithium ion, sodium ion, potassium ion) and organic cation (e.g.,tetramethylammonium ion, tetramethylguanidinium ion,tetramethylphosphonium).

A and B each may have a substituent as long as the conditions (a) to (c)are satisfied, and specific examples thereof include an azo group, ahalogen atom, an alkyl group (including a cycloalkyl group), an alkenylgroup (including a cycloalkenyl group), an alkynyl group, an aryl group,a heterocyclic group, a cyano group, a hydroxyl group, a nitro group, acarboxyl group, an alkoxy group, an aryloxy group, a silyloxy group, aheterocyclic oxy group, an acyloxy group, a carbamoyloxy group, analkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group(including an anilino group), an acylamino group, an aminocarbonylaminogroup, an alkoxycarbonylamino group, an aryloxycarbonylamino group, asulfamoylamino group, an alkylsulfonylamino group, an arylsulfonylaminogroup, a mercapto group, an alkylthio group, an arylthio group, aheterocyclic thio group, a sulfamoyl group, a sulfo group, analkylsulfinyl group, an arylsulfinyl group, an alkylsulfonyl group, anarylsulfonyl group, an acyl group, an aryloxycarbonyl group, analkoxycarbonyl group, a carbamoyl group, an arylazo group, aheterocyclic azo group, an imido group, a phosphino group, a phosphonogroup, a phosphinyl group, a phosphinyloxy group, a phosphinylaminogroup and a silyl group. Among these, preferred are a halogen atom, aheterocyclic group, a cyano group, a nitro group, a carboxyl group, anacyloxy group, a carbamoyloxy group, an alkoxycarbonyloxy group, anaryloxycarbonyloxy group, a sulfamoyl group, a sulfo group, analkylsulfinyl group, an arylsulfinyl group, an alkylsulfonyl group, anarylsulfonyl group, an acyl group, an aryloxycarbonyl group, analkoxycarbonyl group, a carbamoyl group, an imido group, a phosphorylgroup, a phosphono group, a phosphinoyl group, a phosphonyl group, aphosphinoyloxy group, a phosphinoylamino group. In the case where thesubstituent is an azo group, the dye of formula (1) represents a disazodye, a trisazo dye or the like and this dye is preferred as a black dye.

In particular, the substituent is preferably an electron-withdrawinggroup, more preferably a substituent having a up value of 0.40 or more.Examples of the substituent having a σp value of 0.40 or more include acyano group, a nitro group, a carboxyl group, a sulfamoyl group, analkylsulfinyl group, an arylsulfinyl group, an alkylsulfonyl group, anarylsulfonyl group, an acyl group, an aryloxycarbonyl group, analkoxycarbonyl group, a carbamoyl group, an imido group, a phosphonogroup, a phosphoryl group, an electron-withdrawing group-substitutedalkyl group (e.g., trihalomethyl group, perfluoroalkyl group,dicyanomethyl group, iminomethyl group), an electron-withdrawinggroup-substituted alkenyl group (e.g., tricyanovinyl group) and aquaternary salt substituent (e.g., sulfonium group, ammonium group,phosphonium group). Among these functional group, those having ahydrogen atom may be substituted by the above-described group aftereliminating the hydrogen atom. Examples of such a substituent include analkylcarbonylaminosulfonyl group, an arylcarbonylaminosulfonyl group, analkylsulfonylaminocarbonyl group and an arylsulfonylaminocarbonyl group.

The substituents on the heterocyclic ring may combine with each other toform a condensed ring with the heterocyclic ring and the condensed ringmay have a substituent thereon.

In the present invention, an electron-withdrawing group is preferablyintroduced into the dye skeleton to render the oxidation potentialnobler so as to reduce the reactivity with ozone which is anelectrophilic agent. The oxidation potential of the dye is preferably1.0 V or more. When this is described using a Hammett's substituentconstant up value as a measure for the electron withdrawing or donatingproperty of the substituent, the reactivity with ozone can be decreasedby introducing a substituent having a large up value, such as nitrogroup, cyano group, sulfinyl group, sulfonyl group and sulfamoyl group.

The Hammett's substituent constant up value is briefly described. TheHammett's rule is a rule of thumb advocated by L. P. Hammett in 1935 soas to quantitatively discuss the effect of substituent on the reactionor equilibrium of benzene derivatives and its propriety is widelyadmitted at present. The substituent constant determined by theHammett's rule includes a up value and a cm value and these values canbe found in a large number of general publications but these aredescribed in detail, for example, in J. A. Dean (compiler), Lange'sHandbook of Chemistry, 12th ed., McGraw-Hill (1979), and Kagakuno Ryoiki(Chemistry Region), special number, No. 122, pp. 96-103, Nankodo (1979).

In addition to the above-described substituent, when a larger number ofatoms having a high electron negativity are contained as a constituentatom of the chromophore, the reactivity with ozone can be generally moredecreased.

Accordingly, the reactivity with ozone can be more decreased by using,for example, an unsaturated heterocyclic ring than an aryl group as aconstituent element of the chromophore.

Examples of the heteroatom having a high electron negativity include anitrogen atom, an oxygen atom and a sulfur atom. Among these, a nitrogenatom is preferred.

Therefore, the azo dye for use in the present invention is preferably adye where the chromophore is constituted by a heteroatom or contains anunsaturated heterocyclic ring or an electron-withdrawing group.

The electron-withdrawing substituent is preferably a substituent havinga Hammett's σp value of 0.4 or more, more preferably 0.45 or more, andmost preferably 0.50 or more. In the case where a plurality ofelectron-withdrawing groups are present as the substituent on thechromophore, the sum total of up values of the substituents ispreferably 0.50 or more, more preferably 0.60 or more, and mostpreferably 0.70 or more. Specific examples of the electron-withdrawinggroup having a up value of 0.40 or more include those described in J. A.Dean (compiler), Lange's Handbook of Chemistry, 12th ed., McGraw-Hill(1979), and Kagakuno Ryoiki (Chemistry Region), special number, No. 122,pp. 96-103, Nankodo (1979).

As long as formula (1) is satisfied, the dye can be used in the presentinvention irrespective of the color of the dye. The azo dye of thepresent invention is particularly useful and preferably used as amagenta dye, a black dye or a yellow dye. The black dye is preferably adisazo dye or a trisazo dye.

In the case of using the present invention for the formation of a fullcolor image, the image is formed using an ink set comprising, as minimumconstituent elements, at least one yellow ink containing a yellow dye,at least one magenta ink containing a magenta dye and at least one cyanink containing a cyan dye. At least one of the azo dyes used ispreferably the azo dye represented by formula (1) and at least a yellowor magenta color ink preferably contains the azo dye represented byformula (1). More preferably, all azo dyes used are the dye of formula(1). In addition, the black dye is also preferably the azo dye offormula (1) but this dye may be a self-dispersing carbon black describedin JP-A-2001-89688 (the term “JP-A” as used herein means an “unexaminedpublished Japanese patent application”).

In general, a phthalocyanine dye is preferably used as the cyan dye butin view of balance of discoloration with the azo dye of the presentinvention, a cyan dye represented by the following formula (3) ispreferred.

wherein X₁ to X₁₄ each independently represents an electron-withdrawinggroup having a σp value of 0.40 or more, Y₁₁ to Y₁₈ each independentlyrepresents a monovalent substituent, preferably a hydrogen atom, Mrepresents a hydrogen atom, a metal element or its oxide, hydroxide orhalide, and a₁₁ to a₁₄ each independently represents an integer of 1 or2.

When the dye is a water-soluble dye, an ionic hydrophilic group ispreferably further present as a substituent at any position on X₁₁ toX₁₄ or on Y₁₁ to Y₁₈. Examples of the ionic hydrophilic group as asubstituent include those described above.

Preferred examples of the dye which can be used in the present inventionare set forth below, however, these are shown only for describing thepresent invention in detail and the present invention is not limitedthereto.

R Y-1 —NHC₂H₄SO₃Na Y-2

Y-3

Y-4

Y-5 —NHC₆H₁₃ Y-6 —N(C₄H₉)₂

Ar Y-7

Y-8

Y-9

Y-10

Y-11

Y-12

R R′ Y-13 Ph H Y-14 CH₃ H

R Y-15 H Y-16 OH Y-17 SO₃Na

R Y-18 H Y-19 CH₃ Y-20 Ph Y-21 SCH₂COONa Y-22 SCH₂CHMe₂ Y-23 SC₂H₄OC₂H₅

R Y-24 —NHC₂H₄COOK Y-25

Y-26

Y-27 —N(C₄H₉(n))₂ Y-28

Y-29

R₁ R₂ R₃ M-1

M-2

M-3

M-4

M-5

R₁ R₂ R₃ M-6

M-7

M-8

M-9

C₈H₁₇(t) M-10

R₁ R₂ R₃ R₄ M-11

M-12

M-13

M-14

M-15

M-16

M-17

R₁ R₂ R₃ R₄ M-18

M-19

—SO₂CH₃

M-20

—COCH₃ C₈H₁₇(t) C₈H₁₇(t) M-21

—SO₂CH₃

C₈H₁₇(t) M-22

H

M-23

H

M-24

H

M-25

R₁ R₂ R₃ R₄ M-26

M-27

M-28

M-29

M-30

C₈H₁₇(t)

R₁ R₂ R₃ R₄ M-31

M-32

M-33

M-34

M-35

R₁ R₂ R₃ R₄ M-36

M-37

M-38

M-39

M-40

R₁ R₂ R₃ R₄ R₅ R₆ R₇ R₈ M-41

CN

H CONH₂ SO₂CH₃

M-42

Br

COOEt H

C₈H₁₇(t) COCH₃ M-43

SO₂CH₃

CONH₂ H

M-44

CN

H H

SO₂CH₃ M-45

Br

H CONH₂

M-46

CN

CH₃ H

R₁ R₂ R₃ R₄ R₅ R₆ M-47 CH₃ CH₃ CN H

M-48 CH₃ CH₃ CN H

M-49 CH₃ CH₃ CONH₂ H

M-50 CH₃ CH₃ H H

M-51 CH₃ H CN H

R₁ R₂ R₃ R₄ R₅ R₆ M-52 CH₃ CH₃ H

M-53 CH₃ CH₃ H

M-54 CH₃ H H SO₂CH₃

R₁ R₂ R₃ R₄ R₅ R₆ M-55 —SCH₃ CH₃ CN H (C₈H₁₇(t)

M-56

H CONH₂ H

M-57

CH₃ H

M-58 —CH₃ CH₃ H

M-59

H H

(C₈H₁₇(t)

R₁ R₂ R₃ R₄ R₅ R₆ M-60 Me CH₃ CN H

M-61 Me CH₃ CN H

M-62 Me H H

M-63 Ph CH₃ CONH₂ H

M-64 Ph CH₃ H

R₁ R₂ R₃ R₄ R₅ R₆ M-65 5-Cl CH₃ CONH₂ H C₈H₁₇(t) C₈H₁₇(t) M-66 5,6-diClH H

M-67 5.5-diCl CH₃ H

COCH₃ M-68 5-CH₃ H CN H

M-69 5-NO₂ CH₃ H SO₂CH₃

R₁ R₃ R₄ R₅ R₆ M-72

H CH₃ H M-73

H H H M-74

H CH₃ CN M-75

SO₂CH₃ CH₃ H M-76

H H M-77

H CH₃ CN M-78

H CH₃ CN M-79

H CH₃ CN M-80

H CH₃ CN

A B C (BK-1)

(BK-2)

(BK-3)

(BK-4)

(BK-5)

(BK-6)

(BK-7)

(BK-8)

(BK-9)

(BK-10)

(BK-11)

(BK-12)

(BK-13)

(BK-14)

(BK-15)

(BK-16)

(BK-17)

(BK-18)

(BK-19)

(BK-20)

(BK-21)

In the following Tables, specific examples of each pair of (X₁, X₂),(Y₁₁, Y₁₂), (Y₁₃, Y₁₄), (Y₁₅, Y₁₆) and (Y₁₇, Y₁₈) are independently inan irregular order.

No. M X₁ X₂ Y₁₁, Y₁₂ Y₁₃, Y₁₄ Y₁₅, Y₁₆ Y₁₇, Y₁₈ C-1 Cu—SO₂—NH—CH₂—CH₂—SO₃Li —H —H, —H —H, —H —H, —H —H, —H C-2 Cu

—H —Cl, —H —Cl, —H —Cl, —H —Cl, —H C-3 Cu

—H —H, —H —H, —H —H, —H —H, —H C-4 Cu

—H —H, —H —H, —H —H, —H —H, —H C-5 Ni

—H —Cl, —H —Cl, —H —Cl, —H —Cl, —H C-6 Cu—SO₂—NH—CH₂—CH₂—SO₂—NH—CH₂—COONa —CN —H, —H —H, —H —H, —H —H, —H C-7 Cu

—H —H, —H —H, —H —H, —H —H, —H C-8 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li —H —H, —H—H, —H —H, —H —H, —H C-9 Cu —SO₂—CH₂—CH₂—CH₂—SO₃K —H —H, —H —H, —H —H,—H —H, —H C-10 Cu —SO₂—(CH₂)₅—CO₂K —H —H, —H —H, —H —H, —H —H, —H

No. M X₁ X₂ Y₁₁, Y₁₂ Y₁₃, Y₁₄ Y₁₅, Y₁₆ Y₁₇, Y₁₈ C-11 Cu

—H —H, —H —H, —H —H, —H —H, —H C-12 Cu

—SO₃Li —H, —H —H, —H —H, —H —H, —H C-13 Cu

—H —H, —H —H, —H —H, —H —H, —H C-14 Cu

—SO₃Li —H, —H —H, —H —H, —H —H, —H C-15 Cu

—H —H, —H —H, —H —H, —H —H, —H C-16 Cu

—H —H, —H —H, —H —H, —H —H, —H C-17 Cu

—H —H, —H —H, —H —H, —H —H, —H

No. M X₁ X₂ Y₁₁, Y₁₂ Y₁₃, Y₁₄ Y₁₅, Y₁₆ Y₁₇, Y₁₈ C-18 Cu

—H —H, —H —H, —H —H, —H —H, —H C-19 Cu

—H —H, —H —H, —H —H, —H —H, —H C-20 Cu

—H —H, —H —H, —H —H, —H —H, —H C-21 Cu

—H —H, —H —H, —H —H, —H —H, —H C-22 Cu

—H —H, —H —H, —H —H, —H —H, —H C-23 Cu —SO₂NH—C₈H₁₇(t) —H —H, —H —H, —H—H, —H —H, —H C-24 Cu

—H —H, —H —H, —H —H, —H —H, —H

No. M X₁ X₂ Y₁₁, Y₁₂ Y₁₃, Y₁₄ Y₁₅, Y₁₆ Y₁₇, Y₁₈ C-25 Cu

—H —H, —H —H, —H —H, —H —H, —H C-26 Cu

—H —H, —H —H, —H —H, —H —H, —H C-27 Cu

—H —H, —H —H, —H —H, —H —H, —H C-28 Zn

—CN —H, —H —H, —H —H, —H —H, —H C-29 Cu

—H —Cl, —H —Cl, —H —Cl, —H —Cl, —H C-30 Cu

—H —H, —H —H, —H —H, —H —H, —H C-31 Cu

—H —H, —H —H, —H —H, —H —H, —H

No. M X₁ X₂ Y₁₁, Y₁₂ Y₁₃, Y₁₄ Y₁₅, Y₁₆ Y₁₇, Y₁₈ C-32 Cu

—H —H, —H —H, —H —H, —H —H, —H C-33 Cu

—H —H, —H —H, —H —H, —H —H, —H C-34 Cu

—H —H, —H —H, —H —H, —H —H, —H C-35 Cu

—H —H, —H —H, —H —H, —H —H, —H C-36 Cu

—H —H, —H —H, —H —H, —H —H, —H

No. M X₁ X₂ Y₁₁, Y₁₂ Y₁₃, Y₁₄ Y₁₅, Y₁₆ Y₁₇, Y₁₈ C-37 Cu

—H —H, —H —H, —H —H, —H —H, —H C-38 Cu

—H —H, —H —H, —H —H, —H —H, —H C-39 Cu

—Cl —H, —H —H, —H —H, —H —H, —H C-40 Cu

—H —H, —H —H, —H —H, —H —H, —H

No. M X₁ X₂ Y₁₁, Y₁₂ Y₁₃, Y₁₄ Y₁₅, Y₁₆ Y₁₇, Y₁₈ C-41 Cu

—H —H, —H —H, —H —H, —H —H, —H C-42 Cu

—H —H, —H —H, —H —H, —H —H, —H C-43 Cu

—H —H, —H —H, —H —H, —H —H, —H C-44 Cu

—H —H, —H —H, —H —H, —H —H, —H C-45 Cu —SO₂CH₂CH₂OCH₂CH₂OCH₂CH₂SO₃Li —H—H, —H —H, —H —H, —H —H, —H

In the following Tables, introduction sites of substituents (R₁) and(R₂) are in an irregular order within the β-position substitution type.M—Pc(R₁)_(m)(R₂)_(n) No. M R₁ m R₂ n C-46 Cu

3

1 C-47 Cu —SO₂—NH—CH₂—CH₂SO₃Li 3

1 C-48 Cu

3 —SO₂NH—CH₂—CH₂—CH₂—SO₂—NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 C-49 Cu

2 —SO₂—NH—CH₂—CH₂—CH₂—CO—N

CH₂—CH₂—OH)₂ 2 C-50 Cu —SO₂—NH—CH₂—CH₂—SO₂—NH—CH₂CH₂—COONa 3

1 C-51 Cu

3 —SO₂NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 C-52 Cu

2.5 —SO₂—CH₂—CH₂—O—CH₂—CH₂—OH 1.5 C-53 Cu

2 —SO₂—CH₂—CH₂—CH₂—CO—N

CH₂—CH₂—OH)₂ 2 C-54 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 C-55 Cu —SO₂—CH₂—CH₂—CH₂—COOK 2

2 C-56 Cu —SO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 C-57 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—SO₃Li 2

2

M—Pc(R₁)_(m)(R₂)_(n) No. M R₁ m R₂ n C-58 Cu

3

1 C-59 Cu —SO₂NHCH₂CH₂—SO₃Li 3

1 C-60 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—SO₃Na 3

1 C-61 Cu —SO₂CH₂CH₂CH₂SO₃Li 3

1 C-62 Cu —SO₂CH₂CH₂CH₂SO₃Li 2 —SO₂CH₂CH₂OCH₂CH₂OCH₂CH₂OH 2 C-63 Cu—SO₂CH₂CH₂CH₂SO₃K 3

1 C-64 Cu —SO₂CH₂CH₂CH₂SO₃Li 2 —SO₂CH₂CH₂CH₂SO₂N(CH₂CH₂OH)₂ 2 C-65 Cu—CO—NH—CH₂—CH₂—SO₃K 3 —CO—NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 C-66 Cu—CO—NH—CH₂—CH₂—SO₂—NH—CH₂—CH₂—COONa 3

1 C-67 Cu

2.5 —CO—NH—CH₂—CH₂—CH₂—CO—N

CH₂—CH₂—OH)₂ 1.5 C-68 Cu

2 —CO—CH₂—CH₂—CH₂—CO—N

CH₂—CH₂—OH)₂ 2 C-69 Cu —CO₂—CH₂—CH₂—CH₂—SO₃Li 3

1 C-70 Cu —CO₂—CH₂—CH₂—CH₂COOK 2

2

M—Pc(R₁)_(m)(R₂)_(n) No. M R₁ m R₂ n C-71 Cu—CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—SO₃Na 3

1 C-72 Cu —SO₂CH₂CH₂OCH₂CH₂O—CH₂CH₂SO₃K 2

2 C-73 Cu

2

2 C-74 Cu

3

1 C-75 Cu —SO₂(CH₂)₃SO₂NH(CH₂)₃N(CH₂CH₂OH)₂ 2

2 C-76 Cu

3

1 C-77 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 2

1 C-78 Cu —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—OH 3

1 C-79 Cu

2

2 C-80 Cu

3 —SO₂NH—CH₂—CH₂—SO₂NH—CH₂—CH₂—O—CH₂—CH₂—OH 1 C-81 Cu

3

1 C-82 Cu

2.5

1.5

M—Pc(R₁)_(m)(R₂)_(n) No. M R₁ m R₂ n C-83 Cu

2 —SO₂—CH₂—CH₂—CH₂SO₂—NH—(CH₂)₃—CH₂—O—CH₂CH₂—OH 2 C-84 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 C-85 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 C-86 Cu

3 —SO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₂—CH₂—OH 1 C-87 Cu

3

1 C-88 Cu

3 —CO₂—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1 C-89 Cu

3

1 C-90 Cu

3 —CO—NH—CH₂—CH₂—O—CH₂—CH₂—O—CH₃ 1[Inkjet Recording Ink]

The inkjet recording ink can be produced by dissolving and/or dispersingthe above-described dye in a lipophilic or aqueous medium. Preferably,an aqueous medium is used. If desired, other additives are containedwithin the range of not impairing the effect of the present invention.Examples of other additives include known additives such as dryinginhibitor (wetting agent), discoloration inhibitor, emulsificationstabilizer, permeation accelerator, ultraviolet absorbent, antiseptic,fungicide, pH adjusting agent, surface tension adjusting agent,defoaming agent, viscosity controlling agent, dispersant, dispersionstabilizer, rust inhibitor and chelating agent. These various additivesare directly added to the ink solution in the case of a water-solubleink. When an oil-soluble dye is used in the form of a dispersion, theadditives are generally added to the dispersion after the preparation ofa dye dispersion but may be added to the oil or aqueous phase at thepreparation.

The drying inhibitor is suitably used for the purpose of preventingoccurrence of clogging due to drying of the inkjet ink at the inkjetting port of a nozzle used for the inkjet recording system.

The drying inhibitor is preferably a water-soluble organic solventhaving a vapor pressure lower than water. Specific examples thereofinclude polyhydric alcohols represented by ethylene glycol, propyleneglycol, diethylene glycol, polyethylene glycol, thiodiglycol,dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6-hexanetriol, acetyleneglycol derivative, glycerin and trimethylolpropane; lower alkyl ethersof polyhydric alcohol, such as ethylene glycol monomethyl(or ethyl)ether, diethylene glycol monomethyl(or ethyl) ether and triethyleneglycol monoethyl(or butyl) ether; heterocyclic rings such as2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinoneand N-ethylmorpholine; sulfur-containing compounds such as sulfolane,dimethylsulfoxide and 3-sulfolene; polyfunctional compounds such asdiacetone alcohol and diethanolamine; and urea derivatives. Among these,polyhydric alcohols such as glycerin and diethylene glycol arepreferred. These drying inhibitors may be used individually or incombination of two or more thereof. The drying inhibitor is preferablycontained in the ink in an amount of 10 to 50 wt %.

The permeation accelerator is suitably used for the purpose of obtaininghigher permeation of the inkjet ink into paper. Examples of thepermeation accelerator which can be used include alcohols such asethanol, isopropanol, butanol, di(tri)ethylene glycol monobutyl etherand 1,2-hexanediol, sodium laurylsulfate, sodium oleate and nonionicsurfactants. A sufficiently high effect can be usually obtained byadding from 5 to 30 wt % of the permeation accelerator to the ink. Thepermeation accelerator is preferably used in an amount within the rangeof causing no blurring of printed letter or no print through.

The ultraviolet absorbent is used for the purpose of improving thepreservability of image. Examples of the ultraviolet absorbent which canbe used include benzotriazole-base compounds described inJP-A-58-185677, JP-A-61-190537, JP-A-2-782, JP-A-5-197075 andJP-A-9-34057, benzophenone-base compounds described in JP-A-46-2784,JP-A-5-194483 and U.S. Pat. No. 3,214,463, cinnamic acid-base compoundsdescribed in JP-B-48-30492 (the term “JP-B” as used herein means an“examined Japanese patent publication”), JP-B-56-21141 andJP-A-10-88106, triazine-base compounds described in JP-A-4-298503,JP-A-8-53427, JP-A-8-239368, JP-A-10-182621 and JP-T-8-501291 (the term“JP-T” as used herein means a published Japanese translation of a PCTpatent application”), compounds described in Research Disclosure No.24239, and compounds of absorbing ultraviolet light and emittingfluorescent light, so-called fluorescent brightening agents representedby stilbene-base compound and benzoxazole-base compound.

The discoloration inhibitor is used for the purpose of improving thepreservability of image. Examples of the discoloration inhibitor whichcan be used include various organic discoloration inhibitors and metalcomplex-base discoloration inhibitors. Examples of the organicdiscoloration inhibitor include hydroquinones, alkoxyphenols,dialkoxyphenols, phenols, anilines, amines, indanes, chromans,alkoxyanilines and heterocyclic rings. Examples of the metal complexinclude nickel complex and zinc complex. More specifically, compoundsdescribed in patents cited in Research Disclosure, Nos. 17643 (ItemsVII-I to VII-J), 15162, 18716 (page 650, left column), 36544 (page 527),307105 (page 872) and 15162, and compounds included in formulae ofrepresentative compounds and in exemplary compounds described inJP-A-62-215272 (pages 127 to 137) can be used.

Examples of the fungicide include sodium dehydro-acetate, sodiumbenzoate, sodium pyridinethione-1-oxide, ethyl p-hydroxybenzoate,1,2-benzisothiazolin-3-one and salts thereof. The fungicide ispreferably used in the ink in an amount of 0.02 to 1.00 wt %.

As the pH adjusting agent, the above-described neutralizer (e.g.,organic base, inorganic alkali) can be used. The pH adjusting agent isused for the purpose of improving the storage stability of the inkjetink and is preferably added to adjust the inkjet ink to a pH of 6 to 10,more preferably to a pH of 7 to 10.

The surface tension adjusting agent includes nonionic, cationic andanionic surfactants. Preferred examples of the surfactant includeanionic surfactants such as fatty acid salt, alkylsulfuric ester salt,alkylbenzenesulfonate, alkylnaphthalenesulfonate, dialkylsulfosuccinate,alkyl-phosphoric ester salt, naphthalenesulfonic acid formalincondensate and polyoxyethylenealkylsulfuric ester salt, and nonionicsurfactants such as polyoxyethylene alkyl ether, polyoxyethylenealkylallyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acidester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylenealkylamine, glycerin fatty acid ester and oxyethylene oxypropylene blockcopolymer. Also, SURFYNOLS (produced by Air Products & Chemicals), whichis an acetylene-base polyoxyethylene oxide surfactant, is preferablyused. In addition, amine oxide-type amphoteric surfactants such asN,N-dimethyl-N-alkylamine oxide are preferred. Furthermore, surfactantsdescribed in JP-A-59-157636 (pages (37) to (38)) and ResearchDisclosure, No. 308119 (1989) can be also used.

As the defoaming agent, for example, a chelating agent represented bythe fluorine- or silicon-containing compound and EDTA can be used, ifdesired.

When the dye of the present invention is oil-soluble, the dye ispreferably dispersed in an aqueous medium by a method where a coloredfine particle containing the dye and an oil-soluble polymer is dispersedin an aqueous medium described in JP-A-11-286637 and Japanese PatentApplication Nos. 2000-78491, 2000-80259 and 2000-62370, or a methodwhere the dye of the present invention dissolved in a high boiling pointorganic solvent is dispersed in an aqueous medium described in JapanesePatent Application Nos. 2000-78454, 2000-78491, 2000-203856 and2000-203857. With respect to the specific method for dispersing the dyeof the present invention in an aqueous medium, the oil-soluble polymer,high boiling point organic solvent and additives used and the amountsthereof, those described in the above patent publications can bepreferably used. Also, the dye which is solid can be dispersed as it isin a fine particle state. At the dispersion, a dispersant or asurfactant can be used. As for the dispersing device, a simple stirrer,an impeller stirring system, an in-line stirring system, a mill system(e.g., colloid mill, ball mill, sand mill, attritor, roll mill, agitatormill), an ultrasonic wave system and a high-pressure emulsificationdispersion system (high-pressure homogenizer and as the commerciallyavailable device, specific examples thereof include Gaulin Homogenizer,Microfluidizer and DeBEE 2000) can be used. The preparation method ofthe inkjet recording ink is described in detail, in addition to theabove patent publications, in JP-A-5-148436, JP-A-5-295312,JP-A-7-97541, JP-A-7-82515, JP-A-7-118584, JP-A-11-286637 and JapanesePatent Application No. 2000-87539 and the methods described in thesepatent publications can be used also for the preparation of the inkjetrecording ink of the present invention.

As the aqueous medium, a mixture comprising water as the main componentand a water-miscible organic solvent added, if desired, can be used.Examples of the water-miscible organic solvent include alcohols (e.g.,methanol, ethanol, propanol, isopropanol, butanol, isobutanol,sec-butanol, tert-butanol, pentanol, hexanol, cyclohexanol, benzylalcohol), polyhydric alcohols (e.g., ethylene glycol, diethylene glycol,triethylene glycol, polyethylene glycol, propylene glycol, dipropyleneglycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol,glycerin, hexanetriol, thiodiglycol), glycol derivatives (e.g., ethyleneglycol monomethyl ether, ethylene glycol monoethyl ether, ethyleneglycol monobutyl ether, diethylene glycol monomethyl ether, diethyleneglycol monobutyl ether, propylene glycol monomethyl ether, propyleneglycol monobutyl ether, dipropylene glycol monomethyl ether, triethyleneglycol monomethyl ether, ethylene glycol diacetate, ethylene glycolmonomethyl ether acetate, triethylene glycol monomethyl ether,triethylene glycol monoethyl ether, ethylene glycol monophenyl ether),amines (e.g., ethanolamine, diethanolamine, triethanolamine,N-methyldiethanolamine, N-ethyldiethanolamine, morpholine,N-ethylmorpholine, ethylenediamine, diethylenetriamine,triethylenetetramine, polyethyleneimine, tetramethyl-propylenediamine)and other polar solvents (e.g., formamide, N, N-dimethylformamide, N,N-dimethylacetamide, dimethyl-sulfoxide, sulfolane, 2-pyrrolidone,N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone,1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone). Thesewater-miscible organic solvents can be used in combination of two ormore thereof.

The inkjet recording ink of the present invention preferably containsfrom 0.2 to 10 parts by weight of the dye of the present invention per100 parts by weight of the ink. Furthermore, the yellow, magenta andcyan inkjet inks of the present invention each may contain two or moredyes in combination. All of these dyes preferably have an oxidationpotential of 1.0 V or more. In the case of using two or more dyes incombination, the total content of the dyes is preferably in theabove-described range.

In recent years, yellow, magenta and cyan inks each is often composed oftwo or more inks differing in the dye concentration so as to obtainhigher image quality. In the present invention, the dyes used in thedeep or light color ink all preferably have an oxidation potentialnobler than 1.0 V.

The viscosity at 25° C. of the inkjet recording ink of the presentinvention is generally from 1 to 40 mPa·s, preferably from 1 to 30mPa·s, more preferably from 1 to 20 mPa·s. The surface tension thereofat 25° C. is, irrespective of dynamic or static surface tension,generally from 20 to 100 mN/m, preferably from 20 to 70 mN/m, morepreferably from 20 to 50 mN/m. The viscosity and the surface tension canbe adjusted by the addition of various additives, for example, aviscosity adjusting agent, a surface tension adjusting agent, aresistivity adjusting agent, a film adjusting agent, an ultravioletabsorbent, an antioxidant, a discoloration inhibitor, a fungicide, arust preventive, a dispersant and a surfactant.

The inkjet recording ink of the present invention is used for theformation of a full color image but for adjusting the color tone, ablack color tone ink may be further used. Examples of the black coloringmaterial which can be used include disazo, trisazo and tetraazo dyes anda dispersion of carbon black.

[Inkjet Recording Method]

According to the inkjet recording method of the present invention, anenergy is provided to the inkjet recording ink and thereby an image isformed on a known image-receiving material, namely, plain paper, resincoated paper, inkjet special paper described, for example, inJP-A-8-169172, JP-A-8-27693, JP-A-2-276670, JP-A-7-276789,JP-A-9-323475, JP-A-62-238783, JP-A-10-153989, JP-A-10-217473,JP-A-10-235995, JP-A-10-337947, JP-A-10-217597 and JP-A-10-337947, film,electrophotographic common paper, cloth, glass, metal, ceramic or thelike.

In forming an image, a polymer latex compound may be used in combinationfor the purpose of giving glossiness or water resistance or improvingthe weather resistance. The timing of imparting the latex compound tothe image-receiving material may be before, after or simultaneous withthe addition of the coloring agent. Accordingly, the site to which thelatex compound added may be in the image-receiving paper or ink, or aliquid material composed of the polymer latex alone may be prepared andused. More specifically, the methods described in Japanese PatentApplication Nos. 2000-363090, 2000-315231, 2000-354380, 2000-343944 and2000-268952 can be preferably used.

The recording paper and recording film for use in the inkjet printingemploying the ink of the present invention are described below. Thesupport which can be used for the recording paper or film is produced,for example, from a chemical pulp such as LBKP and NBKP, a mechanicalpulp such as GP, PGW, RMP, TMP, CTMP, CMP and CGP, a waste paper pulpsuch as DIP, by mixing thereto, if desired, additives such asconventionally known pigment, binder, sizing agent, fixing agent, cationagent and paper strength increasing agent and then sheeting the mixtureusing various devices such as Fourdrinier paper machine and cylinderpaper machine. Other than this support, synthetic paper or plastic filmmay be used. Th thickness of the support is preferably from 10 to 250 μmand the basis weight is preferably from 10 to 250 g/m². An ink-acceptinglayer and a backcoat layer may be provided on the support as it is ormay be provided after providing a size press or anchor coat layer usingstarch, polyvinyl alcohol or the like. The support may also be subjectedto a flattening treatment by a calendering device such as machinecalender, TG calender and soft calender. In the present invention, thesupport is preferably paper or plastic film of which both surfaces arelaminated with polyolefin (for example, polyethylene, polystyrene,polyethylene terephthalate, polybutene or a copolymer thereof) . In thepolyolefin, a white pigment (for example, titanium oxide or zinc oxide)or a tinting dye (for example, cobalt blue, ultramarine or neodymiumoxide) is preferably added.

The ink-accepting layer provided on the support contains a pigment andan aqueous binder. The pigment is preferably a white pigment. The whitepigment includes a white inorganic pigment such as calcium carbonate,kaolin, talc, clay, diatomaceous earth, synthetic amorphous silica,aluminum silicate, magnesium silicate, calcium silicate, aluminumhydroxide, alumina, lithopone, zeolite, barium sulfate, calcium sulfate,titanium dioxide, zinc sulfide and zinc carbonate, and an organicpigment such as styrene-base pigment, acryl-base pigment, urea resin andmelamine resin. The white pigment contained in the ink-accepting layeris preferably a porous inorganic pigment, more preferably a syntheticamorphous silica or the like having a large pore area. The syntheticamorphous silica may be either a silicic acid anhydride obtained by adry production method or a silicic acid hydrate obtained by a wetproduction method, but a silicic acid hydrate is preferred.

Examples of the aqueous binder contained in the ink-accepting layerinclude water-soluble polymers such as polyvinyl alcohol,silanol-modified polyvinyl alcohol, starch, cationized starch, casein,gelatin, carboxymethyl cellulose, hydroxyethyl cellulose,polyvinylpyrrolidone, polyalkylene oxide and polyalkylene oxidederivative, and water-dispersible polymers such as styrene butadienelatex and acryl emulsion. These aqueous binders can be used individuallyor in combination of two or more thereof. In the present invention,among these, polyvinyl alcohol and silanol-modified polyvinyl alcoholare preferred in view of attaching property to the pigment and peelingresistance of the ink-accepting layer.

The ink-accepting layer may contain a mordant, a water-proofing agent, alight fastness enhancer, a surfactant and other additives in addition tothe pigment and the aqueous binder.

The mordant added to the ink-accepting layer is preferably immobilizedand for this purpose, a polymer mordant is preferably used.

The polymer mordant is described in JP-A-48-28325, JP-A-54-74430,JP-A-54-124726, JP-A-55-22766, JP-A-55-142339, JP-A-60-23850,JP-A-60-23851, JP-A-60-23852, JP-A-60-23853, JP-A-60-57836,JP-A-60-60643, JP-A-60-118834, JP-A-60-122940, JP-A-60-122941,JP-A-60-122942, JP-A-60-235134, JP-A-1-161236 and U.S. Pat. Nos.2,484,430, 2,548,564, 3,148,061, 3,309,690, 4,115,124, 4,124,386,4,193,800, 4,273,853, 4,282,305 and 4,450,224. An image-receivingmaterial containing the polymer mordant described in JP-A-1-161236(pages 212 to 215) is particularly preferred. When the polymer mordantdescribed in this patent publication is used, an image having excellentimage quality can be obtained and at the same time, light fastness ofthe image is improved.

The water-proofing agent is effective for water-proofing the image. Thewater-proofing agent is preferably a cationic resin. Examples of thecationic resin include polyamidopolyamine epichlorohydrin,polyethyleneimine, polyaminesulfone, poly-dimethyldiallylammoniumchloride, cation polyacrylamide and colloidal silica. Among thesecationic resins, polyamidopolyamine epichlorohydrin is preferred. Thecontent of the cationic resin is preferably from 1 to 15 wt %, morepreferably from 3 to 10 wt %, based on the entire solid content of theink-accepting layer.

Examples of the light fastness enhancer include zinc sulfate, zincoxide, hindered amine-base antioxidants and benzotriazole-baseultraviolet absorbents such as benzophenone. Among these, zinc sulfateis preferred.

The surfactant functions as a coating aid, a releasability improver, aslipperiness improver or an antistatic agent. The surfactant isdescribed in JP-A-62-173463 and JP-A-62-183457. In place of thesurfactant, an organofluoro compound may be used. The organofluorocompound is preferably hydrophobic. Examples of the organofluorocompound include a fluorine-containing surfactant, an oily fluorine-basecompound (for example, fluorine oil) and a solid fluorine compound resin(for example, ethylene tetrafluoride resin). The organofluoro compoundis described in JP-B-57-9053 (columns 8 to 17), JP-A-61-20994 andJP-A-62-135826. Other additives added to the ink-accepting layer includea pigment dispersant, a thickener, a defoaming agent, a dye, afluorescent brightening agent, an antiseptic, a pH adjusting agent, amatting agent, a hardening agent and the like. The ink-accepting layermay be either one layer or two layers.

In the recording paper or film, a backcoat layer may also be provided.Examples of the component which can be added to this layer include awhite pigment, an aqueous binder and other components. Examples of thewhite pigment contained in the backcoat layer include white inorganicpigments such as precipitated calcium carbonate, heavy calciumcarbonate, kaolin, talc, calcium sulfate, barium sulfate, titaniumdioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminumsilicate, diatomaceous earth, calcium silicate, magnesium silicate,synthetic amorphous silica, colloidal silica, colloidal alumina,pseudo-boehmite, aluminum hydroxide, alumina, lithopone, zeolite,hydrolyzed halloysite, magnesium carbonate and magnesium hydroxide, andorganic pigments such as styrene-base plastic pigment, acryl-baseplastic pigment, polyethylene, microcapsule, urea resin and melamineresin.

Examples of the aqueous binder contained in the backcoat layer includewater-soluble polymers such as styrene/maleate copolymer,styrene/acrylate copolymer, polyvinyl alcohol, silanol-modifiedpolyvinyl alcohol, starch, cationized starch, casein, gelatin,carboxymethyl cellulose, hydroxyethyl cellulose andpolyvinylpyrrolidone, and water-dispersible polymers such as styrenebutadiene latex and acryl emulsion. Other components contained in thebackcoat layer include a defoaming agent, a foam inhibitor, a dye, afluorescent brightening agent, an antiseptic, a water-proofing agent andthe like.

A polymer latex may be added to a constituent layer (including thebackcoat layer) of the inkjet recording paper or film. The polymer latexis used for the purpose of improving film properties, for example,stabilizing the dimension and preventing the curling, adhesion or filmcracking. The polymer latex is described in JP-A-62-245258,JP-A-62-1316648 and JP-A-62-110066. When a polymer latex having a lowglass transition temperature (40° C. or less) is added to a layercontaining a mordant, the layer can be prevented from cracking orcurling. The curling can also be prevented by adding a polymer latexhaving a high glass transition temperature to the backcoat layer.

The ink of the present invention is not limited in the inkjet recordingsystem and is used in a known system such as an electric charge controlsystem of jetting out the ink by using the electrostatic inductionforce, a drop-on-demand system (pressure pulse system) of using anoscillation pressure of a piezoelectric device, an acoustic inkjetsystem of converting electric signals into acoustic beams, irradiatingthe beams on the ink and jetting out the ink by using the radiationpressure, and a thermal inkjet system of heating the ink to form bubblesand utilizing the generated pressure. The inkjet recording systemincludes a system of ejecting a large number of small volumes ofso-called photo-ink having a low concentration, a system designed toimprove the image quality by using a plurality of inks substantiallysame in the color hue but differing in the concentration, and a systemof using colorless transparent ink.

EXAMPLES

The present invention is described in greater detail below by referringto Examples, however, the present invention is not limited to theseExamples.

Example 1 Preparation of Aqueous Ink

Deionized water was added to the following components to make 1 literand the resulting solution was stirred for 1 hour under heating at 30 to40° C. Thereafter, the solution was adjusted to a pH of 9 with 10 mol/Lof KOH and then filtered under reduced pressure through a microfilterhaving an average pore size of 0.25 μm to prepare a light magenta inksolution. <Composition of Light Magenta Ink Solution> Dye (T-1) 7.5g/liter Diethylene glycol 150 g/liter Urea 37 g/liter Glycerin 130g/liter Triethylene glycol monobutyl ether 130 g/liter Triethanolamine6.9 g/liter Benzotriazole 0.08 g/liter SURFYNOL 465 (produced by Air10.5 g/liter Products Japan) PROXEL XL2 (microbicide, produced by 3.5g/liter ICI Japan)

A magenta ink, a light cyan ink, a cyan ink, a yellow ink and a blackink were further prepared by changing the dye species and additives andusing these inks, Ink Set 101 having concentrations shown in Table 1 wasprepared. TABLE 1 Light Light Magenta Magenta Cyan Cyan Yellow Black Dye(g/liter) T-l T-1 T-2 T-2 T-3 T-4 7.5 30.0 8.75 35.0 29.0 20.0 T-5 20.0T-6 20.0 T-3 21.0 Diethylene 150 110 200 130 160 20 glycol (g/liter)Urea (g/liter) 37 46 — — — — Glycerin 130 160 150 180 150 120 (g/liter)Triethylene 130 140 130 140 180 — glycol monobutyl ether (g/liter)Diethylene — — — — — 230 glycol monobutyl ether (g/liter) 2-Pyrro- — — —— — 81 lidone (g/liter) SURFYNOL 10.5 10.0 9.8 10.5 — — 465 (g/liter)SURFYNOL — — — — 8.5 9.8 STG (g/liter) Triethano- 6.9 7.0 6.0 6.3 0.917.9 lamine (g/liter) Benzo- 0.08 0.07 0.08 0.08 0.06 0.06 triazole(g/liter) Proxel XL2 3.5 1.5 1.1 1.2 1.5 1.1 (g/liter)

Ink Sets 102 to 113 were prepared by changing the dye species in each oflight magenta, magenta, light cyan, cyan, yellow and black inks of InkSet 101 as shown in Table 2. In changing the dye, each dye wasfundamentally replaced by an equimolar amount of dye and the dyeconcentration of each ink solution was adjusted to give the sametransmission density as in Ink Set 101. When dyes were used incombination, the dyes were used in equimolar amounts. TABLE 2 Ink LightMagen- Light Set Magenta ta Cyan Cyan Yellow Black Remarks 101 T-1 T-1T-2 T-2 T-3 T-4, Compar- T-5 ison T-6, T-3 102 T-7 T-1 C-8 C-8 T-3 T-4,Compar- T-5 ison T-6, T-3 103 T-1 T-1 C-8 C-8 Y-22 Bk-7 Compar- ison 104M-36 M-36 C-8 C-8 T-3 Bk-7 Compar- ison 105 M-36 M-36 C-8 C-8 Y-22 T-4,Compar- T-5 ison T-6, T-3 106 M-36 M-36 C-8 C-8 Y-22 Bk-7 Inven- tion107 M-36 M-40 C-8 C-1 Y-22 Bk-9 Inven- tion 108 M-34 M-36 C-18 C-18 Y-2Bk-8 Inven- tion 109 M-36 M-50 C-54 C-54 Y-34 Bk-9 Inven- tion 110 M-36M-12 C-54 C-8 Y-26 Bk-9 Inven- tion 111 M-36 M-32 C-54 C-54 Y-36 Bk-7Inven- tion 112 M-36 M-80 C-54 C-54 Y-59 Bk-9 Inven- tion 113 M-36 M-37C-54 C-54 Y-58  Bk-15 Inven- tion 114 M-36 M-36 C-8 C-8 Y-22 BlackInven- Ink A tion

Dyes T-1 to T-7 for comparison in Tables 1 and 2 are below.

(Image Recording and Evaluation)

Ink Sets 101 to 113 each was filled in a cartridge of an inkjet printerPM770C (manufactured by Seiko Epson Corporation) and an image andletters were printed on Inkjet Paper PM produced by Seiko EpsonCorporation using the same printer. The following evaluations wereperformed.

<Light Fastness>

The chromaticity (a*1, b*1) and lightness (L1) immediately after theprinting were measured using SPM100-II manufactured by Gretag Corp.Also, after irradiation for 7 days with xenon light (85,000 lux) using aweather meter manufactured by Atlas Co., the chromaticity (a*2, b*2) andlightness (L2) were again measured. The color difference (ΔE) betweenbefore and after the light irradiation was obtained according to thefollowing formula and evaluated.ΔE={(a*1−a*2)²+(b*1−b*2)²+(L1−L2)²}^(1/2)

The color difference was evaluated at three points having a reflectiondensity of 1.0, 1.3 and 1.6. The light fastness was rated “A” when thecolor difference was less than 5 at all density points, rated “B” whenthe color difference was less than 5 at two density points, rated “C”when the color difference was less than 5 at one density point, andrated “D” when the color density was 5 or more at all density points.

<Heat Fastness>

The sample was stored for 6 days under the condition of 80° C. and thecolor difference between before and after the storage was evaluated inthe same manner as in the evaluation of light fastness. The dye residualpercentage was evaluated at three points having a reflection density of1.0, 1.3 and 1.6. The heat fastness was rated “A” when the colordifference was less than 3 at all density points, rated “B” when thecolor difference was less than 3 at two density points, rated “C” whenthe color difference was less than 3 at one density point, and rated “D”when the color difference was 3 or more at all density points.

<Ozone Resistance>

The sample was stored in a box set to an ozone gas concentration of 0.5ppm for 7 days and the color difference between before and after thestorage was evaluated in the same manner as in the evaluation of lightfastness. The dye residual percentage was evaluated at three pointshaving a reflection density of 1.0, 1.3 and 1.6. The ozone resistancewas rated “A” when the color difference was less than 10 at all densitypoints, rated “B” when the color difference was less than 10 at twodensity points, rated “C” when the color difference was less than 10 atone density point, and rated “D” when the color difference was 10 ormore at all density points. The ozone gas concentration in the box wasset using an ozone gas monitor (Model OZG-EM-01) manufactured byAPPLICS. TABLE 3 Ink Set Light Fastness Heat Fastness Ozone Resistance101 D D D 102 C C C 103 C B C 104 B B C 105 B B B 106 A A A 107 A A A108 A A A 109 A A A 110 A A A 111 A A A 112 A A A 113 A A A 114 A A A

It is seen from the results shown in Table 3 that when the inkcomposition of the present invention is used, excellent performance isobtained particularly in the fastness.

The same effect as above is obtained even when the image-receiving paperused in the present invention is changed to Inkjet Paper GASAI PhotoFinish produced by Fuji Photo Film Co., Ltd. or PR101 produced by CanonInc.

Example 2

The same ink as produced in Example 1 was filled in an inkjet printerBJ-F850 (manufactured by Canon Inc.) and an image was printed on InkjetPaper GASAI Photo Finish produced by Fuji Photo Film Co., Ltd. in thesame printer and evaluated in the same manner as in Example 1, as aresult, similar results to those in Example 1 were obtained. Also, thesame effect as above was obtained even when the image-receiving paperwas changed to PM photographic paper produced by Seiko Epson Corporationor PR101 produced by Canon Inc.

Example 3 Preparation of Black Ink

Bonjet Black CW-1 (produced by Orient Chemical Industries, Ltd.) wasdiluted with water to a pigment concentration of 10 wt % and thencentrifuged (7,000 rpm, 30 minutes) to obtain a pigment dispersionsolution (pigment concentration: 8.3 wt %). Pigment dispersion preparedabove 50 wt % Diethylene glycol 15 wt % Urea 5 wt % C₄H₉(CH₂CH₂O)₂H 2 wt% Surfactant (OLIFIN E1010, produced by 1 wt% Nisshin Kagaku) Pure water27 wt %

While thoroughly mixing these components, 1N of an aqueous sodiumhydroxide solution was added dropwise until the pH reached 7.5. Theresulting solution was filtered under pressure through a 1-μm filter toobtain Black Ink A comprising a self-dispersible pigment.

Ink Set 114 was prepared in the same manner as Ink Set 106 of Example 1except for changing the black ink of Ink Set 106 to Black Ink A preparedabove using a self-dispersible pigment. Then, printing and evaluationwere performed in the same manner as in Example 1. The results are shownin Table 3. It is seen that even a pigment is used as the black dye, thecolor balance is free from serious disruption due to discoloration bylight or ozone.

Example 4

Ink Set 201 was prepared by changing the light magenta, magenta, lightcyan, cyan and yellow inks in Ink Set 101 of Example 1 to oil-solubledye inks prepared as follows.

Dye (M-26) (8 g) and 60 g of a surfactant (Emal 20C, trade name,produced by Kao Corporation) were dissolved in 6 g of high boiling pointorganic solvent (S-1), 10 g of high boiling point organic solvent (S-2),1.0 g of additive (A-1) and 50 ml of ethyl acetate at 70° C. To theresulting solution, 500 ml of deionized water was added while stirringwith a magnetic stirrer to produce an oil-in-water coarse particledispersion.

This coarse particle dispersion was passed 5 times throughMicrofluidizer (manufactured by Microfluidex Inc.) under a pressure of60 MPa to form the coarse particles into fine particles. The resultingemulsified product was then treated in a rotary evaporator to remove thesolvent until the odor of ethyl acetate was not generated.

To the thus-obtained finely emulsified product of hydrophobic dye, 140 gof diethylene glycol, 64 g of glycerin and additives such as urea wereadded. Then, deionized water was added to make a total amount of 1 literand the pH was adjusted to 9 with 10 mol/liter of KOH to prepare a lightmagenta ink having a concentration shown in Table 4. The volume averageparticle size of the obtained emulsification dispersion ink was measuredby Microtrac UPA (manufactured by Nikkiso) and found to be 40 nm.

Furthermore, a magenta ink, a light cyan ink, a cyan ink and a yellowink of Ink Set 201 shown in Table 4 were prepared by changing the kindand amount of the dye used, the amount of the high boiling point organicsolvent used and the kind and amount of each additive used. Here, inTable 4, a composition of the final composition product after theevaporation of solvent is shown.

The black ink used was Bonjet Black CW-1 (produced by Orient ChemicalIndustries, Ltd.) described in Example 3, which is a self-dispersiblepigment. TABLE 4 Light Light Magenta Magenta Cyan Cyan Yellow Dye(g/liter) M-26 M-26 C-26 C-26 Y-42 5.00 20.0 11.2 44.6 27.2 High boilingpoint S-1 14.52 8.1 32.4 20.0 organic solvent 3.75 25.52 14.3 57.1 34.5(g/liter) S-2 6.25 Additive A-1 0.625 2.5 1.2 4.8 3.2 (g/liter) Emal 20C(g/liter) 38.0 120 46.5 186.0 150 Diethylene glycol 87.5 87.5 87.5 87.587.5 (g/liter) Glycerin (g/liter) 40 40 40 40 40 SURFYNOL 465 10.0 10.010.0 10.0 10.0 (g/liter) Triethanolamine 7.5 7.5 7.5 7.5 7.5 (g/liter)Benzotriazole 0.075 0.075 0.075 0.075 0.075 (g/liter) Proxel XL2(g/liter) 2.5 2.5 2.5 2.5 2.5 Deionized water was added to make 1 liter.Volume average 40 nm 45 nm 35 nm 41 nm 38 nm particle size

Solvents S-1 and S-2 and Additive A-1 in Table 4 are shown below.

Ink Sets 202 to 212 were produced in the same manner as Sample 201except for changing the dye species in each ink solution as shown inTable 5 below. In changing the dye, the dye is basically changed by anequimolar amount of a dye and the dye concentration of each ink solutionwas adjusted to give the same transmission density as in Ink Set 201.TABLE 5 Ink Light Light Set Magenta Magenta Cyan Cyan Yellow Remarks 201M-26 M-26 C-26 C-26 Y-42 Invention 202 M-28 M-28 C-26 C-26 Y-42 ″ 203M-29 M-26 C-27 C-26 Y-42 ″ 204 M-31 M-31 C-26 C-26 Y-42 ″ 205 M-41 M-26C-26 C-26 Y-42 ″ 206 M-26 M-26 C-32 C-26 Y-43 ″ 207 M-27 M-27 C-26 C-78Y-43 ″ 208 M-26 M-26 C-76 C-84 Y-44 ″ 209 M-59 M-59 C-26 C-26 Y-45 ″ 210T-8 T-8 C-26 C-26 T-9 Comparison 211 T-10 T-10 C-26 C-26 T-9 ″ 212 T-8T-8 T-11 T-11 T-9 ″

Dyes T-8 to T-11 for comparison in Table 5 are shown below.

Ink Sets 201 to 209 each was filled in a cartridge of an inkjet printerPM770C (manufactured by Seiko Epson Corporation) and an image wasprinted on Inkjet Paper GASAI Photo Finish produced by Fuji Photo FilmCo., Ltd. using the same printer. The following evaluations wereperformed. Sample 101 of Example 1 was also evaluated under the sameconditions.

<Water Resistance>

The obtained image was dipped in deionized water for 60 seconds and thenthe blurring of image was evaluated with an eye.

The water resistance was rated “A” when the blurring of image was notobserved at all, rated “B” when the blurring was slightly observed, andrated “C” when the blurring was not in an allowable level.

As for the fastness of image, a gray printed sample was produced andevaluated as follows.

<Light Fastness (Light Resistance)>

The chromaticity (a*1, b*1) and lightness (L1) immediately after theprinting were measured using SPM100-II manufactured by Gretag Corp.Also, after irradiation for 14 days with xenon light (85,000 lux) usinga weather meter manufactured by Atlas Co., the chromaticity (a*2, b*2)and lightness (L2) were again measured. The color difference (ΔE)between before and after the light irradiation was obtained according tothe following formula and evaluated.ΔE={(a*1−a*2)²+(b*1−b*2)²+(L1−L2)²}^(1/2)

The color difference was evaluated at three points having a reflectiondensity of 1.0, 1.3 and 1.6. The light fastness was rated “A” when thecolor difference was less than 5 at all density points, rated “B” whenthe color difference was less than 5 at two density points, rated “C”when the color difference was less than 5 at one density point, andrated “D” when the color density was 5 or more at all density points.

<Heat Fastness (Beat Resistance)>

The sample was stored for 6 days under the condition of 85° C. and thecolor difference between before and after the storage was evaluated inthe same manner as in the evaluation of light fastness. The dye residualpercentage was evaluated at three points having a reflection density of1.0, 1.3 and 1.6. The heat fastness was rated “A” when the colordifference was less than 3 at all density points, rated “B” when thecolor difference was less than 3 at two density points, rated “C” whenthe color difference was less than 3 at one density point, and rated “D”when the color difference was 3 or more at all density points.

<Ozone Resistance>

The sample was stored in a box set to an ozone gas concentration of 1.00ppm for 7 days and the color difference between before and after thestorage was evaluated in the same manner as in the evaluation of lightfastness. The dye residual percentage was evaluated at three pointshaving a reflection density of 1.0, 1.3 and 1.6. The ozone resistancewas rated “A” when the color difference was less than 10 at all densitypoints, rated “B” when the color difference was less than 10 at twodensity points, rated “C” when the color difference was less than 10 atone density point, and rated “D” when the color difference was 10 ormore at all density points. The ozone gas concentration in the box wasset using an ozone gas monitor (Model OZG-EM-01) manufactured byAPPLICS. TABLE 6 Water Light Heat Ozone Ink Set Resistance FastnessFastness Resistance 201 A A A A 202 A A A A 204 A A A A 203 A A A A 205A A A A 206 A A A A 207 A A A A 208 A A A A 209 A A A A 210 A B B D 211A B B D 212 A C C D 101 B D D D

It is seen from the results shown in Table 6 that when the inkcomposition of the present invention is used as the oil-soluble dyedispersion, excellent performance is attained particularly in thefastness. Also, excellent performance is attained in the waterresistance which is a problem for a water-soluble ink.

Incidentally, the same effect as above is obtained even when theimage-receiving paper used in the present invention is changed to PMphotographic paper produced by Seiko Epson Corporation or PR101 producedby Canon Inc.

Example 5

The same ink as produced in Example 4 was filled in an inkjet printerBJ-F850 (manufactured by Canon Inc.) and an image was printed on InkjetPaper GASAI Photo Finish produced by Fuji Photo Film Co., Ltd. in thesame printer and evaluated in the same manner as in Example, as aresult, similar results to those in Example 3 were obtained. Also, thesame effect as above was obtained even when the image-receiving paperwas changed to PM photographic paper produced by Seiko Epson Corporationor PR101 produced by Canon Inc.

INDUSTRIAL APPLICABILITY

According to the present invention, an azo dye having a specificstructure capable of drastically solving the ozone discoloration is usedas a dye constituting an ink, whereby an inkjet recording ink capable ofgiving a color image having excellent fastness to ozone gas is providedand an ink set for inkjet recording and an inkjet recording method,which can form an image having excellent color reproducibility and highlight fastness, are provided.

1. An ink for inkjet recording, comprising at least one compoundselected from azo dyes represented by the following formula (1):A−N=N−B wherein A and B each independently represents an aromatic group,or a 5- or 6-membered unsaturated heterocyclic group, provided that asubstituent on each ring of A and B, which is located at a conjugatedposition with respect to the azo group, satisfies the followingconditions (a) to (c): (a) the substituent is not a hydroxyl group, (b)when the substituent is an amino group, the amino group does not have ahydrogen atom at the α-position, and (c) when the substituent is anether group, the ether group does not have a hydrogen atom at theα-position.
 2. The ink for inkjet recording as claimed in claim 1,wherein at least one of A and B in the formula (1) represents a 5- or6-membered unsaturated heterocyclic group.
 3. The ink for inkjetrecording as claimed in claim 1, wherein the azo dye represented by theformula (1) contains an electron-withdrawing group.
 4. The ink forinkjet recording as claimed in claim 1, wherein the amino group nothaving a hydrogen atom at the α-position is an amino group substitutedby a tertiary alkyl group, an aryl group, a heterocyclic group or anunsubstituted amino group.
 5. The ink for inkjet recording as claimed inclaim 1, wherein the ether group not having a hydrogen atom at theα-position is an aryloxy group or a heteryloxy group.
 6. An ink set forinkjet recording, comprising: a yellow ink containing at least oneyellow dye; a magenta ink containing at least one magenta dye; and acyan ink containing at least one cyan dye, wherein at least one dye ofthe yellow, magenta and cyan dyes contains an azo dye represented by thefollowing formula (1):A−N=N−B wherein A and B each independently represents an aromatic group,or a 5- or 6-membered unsaturated heterocyclic group, provided that asubstituent on each ring of A and B, which is located at a conjugatedposition with respect to the azo group, satisfies the followingconditions (a) to (c): (a) the substituent is not a hydroxyl group, (b)when the substituent is an amino group, the amino group does not have ahydrogen atom at the α-position, and (c) when the substituent is anether group, the ether group does not have a hydrogen atom at theα-position.
 7. The ink set for inkjet recording as claimed in claim 6,wherein at least one of A and B in the formula (1) represents a 5- or6-membered unsaturated heterocyclic group.
 8. The ink set for inkjetrecording as claimed in claim 6, wherein the azo dye represented by theformula (1) contains an electron-withdrawing group.
 9. The ink set forinkjet recording as claimed in claim 6, wherein the amino group nothaving a hydrogen atom at the a-position is an amino group substitutedby a tertiary alkyl group, an aryl group, a heterocyclic group or anunsubstituted amino group.
 10. The ink set for inkjet recording asclaimed in claim 6, wherein the ether group not having a hydrogen atomat the α-position is an aryloxy group or a heteryloxy group.
 11. The inkset for inkjet recording as claimed in claim 6, wherein the cyan dyeincludes a cyan dye represented by the following formula (3):

wherein X₁₁ to X₁₄ each independently represents an electron-withdrawinggroup having a σp value of 0.40 or more; Y₁₁ to Y₁₈ each independentlyrepresents a monovalent substituent; M represents a hydrogen atom, ametal element or its oxide, hydroxide or halide; a₁₁ to a₁₄ eachindependently represents an integer of 1 or
 2. 12. An ink set for inkjetrecording, comprising: a yellow ink containing at least one yellow dye;a magenta ink containing at least one magenta dye; a cyan ink containingat least one cyan dye; and a black ink containing at least one blackdye, wherein at least one dye of the yellow, magenta, cyan and blackdyes contains an azo dye represented by the following formula (1):A−N=N−B wherein A and B each independently represents an aromatic group,or a 5- or 6-membered unsaturated heterocyclic group, provided that asubstituent on each ring of A and B, which is located at a conjugatedposition with respect to the azo group, satisfies the followingconditions (a) to (c): (a) the substituent is not a hydroxyl group, (b)when the substituent is an amino group, the amino group does not have ahydrogen atom at the α-position, and (c) when the substituent is anether group, the ether group does not have a hydrogen atom at theα-position.
 13. An inkjet recording method comprising forming an imageusing the ink for inkjet recording claimed in claim
 1. 14. An inkjetrecording method comprising forming an image using the ink set forinkjet recording claimed in claim
 6. 15. An inkjet recording methodcomprising forming an image using the ink set for inkjet recordingclaimed in claim
 12. 16. The inkjet recording method as claimed in claim13, which comprises forming an image on an image-receiving materialcomprising a support having thereon an image-receiving layer containinga white inorganic pigment particle.
 17. The inkjet recording method asclaimed in claim 14, which comprises forming an image on animage-receiving material comprising a support having thereon animage-receiving layer containing a white inorganic pigment particle. 18.The inkjet recording method as claimed in claim 15, which comprisesforming an image on an image-receiving material comprising a supporthaving thereon an image-receiving layer containing a white inorganicpigment particle.